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<b>Db::set_append_recno</b>
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<b><pre>
#include &lt;db_cxx.h&gt;
<p>
int
Db::set_append_recno(int (*db_append_recno_fcn)(DB *dbp, Dbt *data, db_recno_t recno));
</pre></b>
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<b>Description: Db::set_append_recno</b>
<p>When using the <a href="../api_cxx/db_put.html#DB_APPEND">DB_APPEND</a> option of the <a href="../api_cxx/db_put.html">Db::put</a> method,
it may be useful to modify the stored data based on the generated key.
If a callback function is specified using the
Db::set_append_recno method, it will be called after the record number
has been selected, but before the data has been stored.</p>
<p>The Db::set_append_recno method configures operations performed using the specified
<a href="../api_cxx/db_class.html">Db</a> handle, not all operations performed on the underlying
database.</p>
<p>The Db::set_append_recno method may not be called after the <a href="../api_cxx/db_open.html">Db::open</a> method is called.
</p>
<p>The Db::set_append_recno method
either returns a non-zero error value
or throws an exception that encapsulates a non-zero error value on
failure, and returns 0 on success.
</p>
<b>Parameters</b> <br>
 <b>db_append_recno_fcn</b><ul compact><li>The <b>db_append_recno_fcn</b> parameter is a function to call after
the record number has been selected but before the data has been stored
into the database.  The function takes three parameters:
<br>
<b><b>db</b></b><ul compact><li>The <b>db</b> parameter is the enclosing database handle.</ul>
<b><b>dbt</b></b><ul compact><li>The <b>dbt</b> parameter is the data <a href="../api_cxx/dbt_class.html">Dbt</a> to be stored.</ul>
<b><b>recno</b></b><ul compact><li>The <b>recno</b> parameter is the generated record number.</ul>
<br>
<p>The called function may modify the data <a href="../api_cxx/dbt_class.html">Dbt</a>.  If the function
needs to allocate memory for the <b>data</b> field, the <b>flags</b>
field of the returned <a href="../api_cxx/dbt_class.html">Dbt</a> should be set to
DB_DBT_APPMALLOC, which indicates that Berkeley DB should free the
memory when it is done with it.</p>
<p>The callback function must return 0 on success and <b>errno</b> or
a value outside of the Berkeley DB error name space on failure.</p>
<p>Berkeley DB is not re-entrant.  Callback functions should not attempt to make
library calls (for example, to release locks or close open handles).
Re-entering Berkeley DB is not guaranteed to work correctly, and the results
are undefined.</p></ul>
<br>
<br><b>Errors</b>
<p>The Db::set_append_recno method
may fail and throw
<a href="../api_cxx/except_class.html">DbException</a>,
encapsulating one of the following non-zero errors, or return one of
the following non-zero errors:</p>
<br>
<b>EINVAL</b><ul compact><li>If the method was called after <a href="../api_cxx/db_open.html">Db::open</a> was called; or if an
invalid flag value or parameter was specified.</ul>
<br>
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<br><b>Class</b>
<a href="../api_cxx/db_class.html">Db</a>
<br><b>See Also</b>
<a href="../api_cxx/db_list.html">Databases and Related Methods</a>
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